Soil Carbon and Nitrogen Fractions and Crop Yields Affected by Residue Placement and Crop Types

High variability in soil properties in the field results in non-response of management practices on soil C and N fractions. We evaluated the effects of crop species (spring wheat [Triticum aestivum L.], pea [Pisum sativum L.], and fallow), N fertilization (0.11 and 0.96 g N pot-1), and residue placement (no residue, surface placement, and incorporation into the soil) on soil C and N fractions in a greenhouse. Soil samples collected from the field were grown with crops in a greenhouse and analyzed for soil organic C (SOC), total N (STN), particulate organic C and N (POC and PON), microbial biomass C and N (MBC and MBN), potential C and N mineralization (PCM and PNM), NH4-N, and NO3-N contents. The 10.1371/journal.pone.0105039lacement under wheat with 0.11 g N pot-1, PNM, MBN, and NO3-N greater in surface residue placement under wheat or fallow with 0.96 g N pot-1, but POC, PON, and NH4-N greater in residue incorporation under wheat with 0.11 to 0.96 g N pot-1 than other treatments. Soil quality responses to short-term management were readily obtained under controlled soil and environmental conditions in the greenhouse.